Stage Recovery for, well, stage recovery—it calculates terminal velocity based on how many parachutes you have and refunds you a percentage of the value based on impact speed and distance from the launch site.
I only get about ~50% value on these ones even before the distance factor—four parachutes is only enough to slow the stage to ~10m/s. Each booster runs about 20,000 kerbucks, and I get ~8,000 back each. (It’s asparagus-staged, so a little more for the first two off, which land closer, and a little less for the last two.) After the last two side boosters separate, it dips down to about 0.7 TWR for a little while, but it’s high/fast enough by that point that it doesn’t matter.
The side boosters are Mainsails, the center booster is a Skipper, the Clipper’s transfer stage has three Nervs on an engine plate, and the satellites use the wee little Spark. I don’t recall offhand what the satellites mass, but they’re pretty simple—1-2 batteries, 1-2 solar panels, a small reaction wheel, some science instruments, and a QBE probe core. The single 1.25m tank with the Spark engine yields about 2km/s of delta-v, which is far and away more than I’ll need, and the Spark also has decent specific impulse in atmosphere, so it’s a fine choice for a Duna landing.